JPH10340719A - Alkaline dry battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the strength of a positive electrode, without increasing the content of a binder in a positive electrode material by heating the positive electrode material containing the binder to a temperature near the melting point or the softening point of the binder. SOLUTION: Polyethylene powder is added as a binder to a main positive electrode material, containing electrolytic manganese dioxide, graphite, and an electrolyte comprising a potassium hydroxide aqueous solution. Then they are stirred and mixed. The mixture obtained is pressed, crushed, granulated, and the granulated powder is heated to a temperature near the melting point or the softening point of the binder. The powder is pressed to mold a cylinder, four molded bodies are stacked in a positive can 2, and further heated, so as to bring the molded body into close contact with the positive can 2 to form a positive electrode 1. An AA-size alkaline dry battery is assembled with the positive electrode 1, a separator 3, an electrolyte, and zinc paste. By increasing the binding effect of the binder through heating, the strength of the positive electrode 1 is enhanced, and productivity is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an alkaline dry battery and a method for producing the same.

[0002]

2. Description of the Related Art In general, the positive electrode material of an alkaline dry battery mainly comprises manganese dioxide as a positive electrode active material and graphite as a conductive additive, and contains a binder for imparting binding properties. , Water or electrolyte. The reason why the binder is contained in the positive electrode material is that the positive electrode of the alkaline dry battery absorbs the electrolytic solution after molding or generates a small amount of gas, whereby the binding force between the positive electrode materials is loosened and the conductivity is reduced, This is because the reduction in the discharge duration is suppressed because the discharge duration is reduced, and the productivity is improved by reducing cracking and chipping of the positive electrode during the manufacturing process.

[0003] When the content of the binder in the positive electrode material is increased, the strength of the positive electrode can be increased, the productivity can be improved, and the reduction in the discharge duration time due to storage can be suppressed. On the other hand, the amount of the active material to be charged decreases, and the battery capacity decreases.

Examples of the binder include organic substances having alkali resistance, such as polyethylene, polytetrafluoroethylene (PTFE), sodium polyacrylate (SPA), polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR). However, there is no definitive substance, and the selection of a binder alone cannot solve the reduction of the discharge duration and the reduction of the battery capacity at once.

[0005]

As described above, when the content of the binder in the positive electrode material is increased, the binding effect of the binder can be increased, the strength of the positive electrode is increased, and the productivity is improved. As well as
Although it is possible to prevent a decrease in the duration of discharge due to storage, when the content of the binder in the positive electrode material is increased, the amount of the active material to be filled is reduced, and the battery capacity is reduced.

Accordingly, the present invention solves the above-mentioned problems in the prior art, and increases the binding effect of the binder without increasing the content of the binder in the positive electrode material, thereby improving the productivity. In addition, an object of the present invention is to provide an alkaline dry battery that suppresses a decrease in the duration of discharge due to storage and prevents a decrease in battery capacity.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, when heating a binder-containing positive electrode material near the melting point or softening point of the binder, the binder and the positive electrode were heated. It has been found that the binding property of the active material with manganese dioxide and the like is improved, and the strength of the positive electrode can be increased without increasing the content of the binder in the positive electrode material. I have to do it.

[0008] That is, by heating as described above, the binding effect of the binder is increased, and the strength of the positive electrode can be increased. In addition to improving the battery performance, the swelling of the positive electrode due to the electrolyte during storage of the battery is reduced, and the decrease in conductivity during storage is suppressed, and the decrease in the discharge duration time due to storage is suppressed. In addition, since it is not necessary to increase the content of the binder, a decrease in battery capacity does not occur, and a decrease in battery capacity can be prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the present invention in detail, the general manufacturing process of a positive electrode of a conventional alkaline dry battery will be described. First, as shown in FIG. Mix the binder and water or electrolyte, then
In order to improve the productivity in the next molding step, 10-1
Granulate to about 00 mesh. However, this granulation step is not an essential step and can be omitted. Next, the positive electrode material is formed into a cylindrical shape, and the formed body is inserted into a positive electrode can. Then, when the molded body is inserted into the positive electrode can, or after the molded body is inserted into the positive electrode can, a pressing step is performed to increase the adhesion between the molded body of the positive electrode material and the positive electrode can by applying pressure, and the positive electrode is formed. Is done.

On the other hand, in the present invention, as shown in FIG. 1, after the mixing or granulation, heating is performed (heating), or after molding, before or after insertion into the positive electrode can,
Furthermore, it heats after pressure bonding (heating, heating, heating). This heating is shown in FIG. 1 as “heating”, “heating”,
It may be performed in any of the steps described as “heating” and “heating”, or may be performed in two or more steps. Then, except that this heating is performed, a positive electrode can be manufactured by the same method as the conventional method for manufacturing a positive electrode shown in FIG.

In the present invention, manganese dioxide or the like is used as the positive electrode active material, graphite or the like is used as the conductive aid, and polyethylene, polytetrafluoroethylene, sodium polyacrylate, polyvinyl alcohol, or the like is used as the binder. Styrene butadiene rubber or the like is used, and polyethylene is particularly suitable because it is inexpensive for obtaining a predetermined binding property.

Since heating is performed at a temperature near the melting point or softening point of the binder, the heating temperature varies depending on the binder used, but is generally preferably about 90 to 150 ° C. If the heating temperature is too low, the binding effect of the binder does not increase, and if the heating temperature is too high, the water of crystallization contained in manganese dioxide evaporates, and the properties of manganese dioxide may change and battery performance may be impaired. For example, when polyethylene is used as the binder, the heating temperature is 1
00-140 ° C is preferred. The heating time varies depending on the heating temperature and the type of binder, but is preferably about 3 to 15 minutes.

The amount of the binder used may be the same as that of the conventional one.
It may be contained in an amount of about 5% by weight, and in particular, a relatively small amount of about 0.3 to 0.7% by weight can exert a good binding effect.

By heating the binder near the melting point or softening point of the binder as described above, the binding effect of the binder is increased, the binding between the binder and the positive electrode active material such as manganese dioxide is improved, and the strength of the positive electrode is improved. Of the positive electrode during the manufacturing process is reduced, and the productivity is improved, and the swelling of the positive electrode due to the electrolyte during storage of the battery is reduced, and the decrease in conductivity during storage is suppressed. In addition, a decrease in the discharge duration time due to storage is suppressed.

[0015]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

EXAMPLE 1 89 parts by weight of electrolytic manganese dioxide, graphite and a concentration of 35% by weight
1 part by weight of a polyethylene powder having a softening point of 96 ° C. and an average particle size of 18 μm as a binder was added to 99 parts by weight of a main positive electrode material containing an electrolytic solution composed of an aqueous solution of potassium hydroxide and stirred and mixed. After the obtained mixture was pressed and pulverized, the mixture was granulated to a size of 50 mesh pass, and the obtained granulated powder was heated at 140 ° C. for 5 minutes. Next, after being formed into a cylindrical shape by a press machine, four of the formed bodies were inserted into a positive electrode can so as to be stacked, and the above-mentioned formed body was pressed on the positive electrode can by further pressurization to form a positive electrode. Using this positive electrode, a known separator, an electrolytic solution, a zinc paste and the like, an AA alkaline battery having the structure shown in FIG. 2 was produced.

Here, the alkaline dry battery shown in FIG. 2 will be described. As for the positive electrode 1, polyethylene is used as a binder as described above, and after granulation, a heated positive electrode material is formed into a cylindrical shape. The positive electrode can 2 is stacked, inserted into the positive electrode can 2 with terminals, and pressurized from above to press the molded body of the positive electrode material onto the inner surface of the positive electrode can 2.

The separator 3 is disposed between the positive electrode 1 and the negative electrode 4 made of zinc paste. The zinc paste is made of a zinc powder and a potassium hydroxide aqueous solution to which a gelling agent is added to form a gelled alkaline electrolyte. The tip end side of the negative electrode current collector 5 is inserted into the negative electrode 4 made of this zinc paste, and the opening of the positive electrode can 2 has the head of the negative electrode current collector 5, a sealing body 6, a metal washer 7, The positive electrode can 2 is sealed with a resin washer 8, an insulating cap 9, a negative electrode terminal plate 10, and the like.

A part of the battery prepared as described above was replaced with 8
It was stored at 0 ° C. for 5 days and 8 days, and used for the measurement of the discharge duration described below.

Example 2 As in Example 1, 99 parts by weight of a main positive electrode material containing electrolytic manganese dioxide, graphite and an electrolytic solution were used as a binder, and the same softening point as in Example 1 was 96 ° C. and the average particle size was 18 μm. Of polyethylene powder was added, and the mixture was stirred and mixed. After granulating the obtained mixture to a size of 50 mesh pass, the mixture is formed into a cylindrical shape by a press machine, and the obtained cylindrical body is formed into a cylindrical shape.
The positive electrode can was inserted into the positive electrode can in a stacked manner, and the molded body of the positive electrode material was press-bonded to the positive electrode can under pressure to obtain a positive electrode.

The positive electrode was heated at 80 ° C, 100 ° C, 120 ° C,
Heated at 140 ° C. and 160 ° C. for 5 minutes each,
Except that these positive electrodes were used, AA alkaline batteries were prepared in the same manner as in Example 1. A part of the battery thus prepared was stored at 80 ° C. for 5 days and 8 days,
It was used for measurement of the discharge duration described later.

Comparative Example 1 An AA alkaline battery was prepared in the same manner as in Example 1 except that heating was not performed as in Example 1 according to the prior art. A part of the produced battery was stored at 80 ° C. for 5 days and 8 days, and was subjected to measurement of a discharge duration time.

After granulating the positive electrode material as in Example 1 above,
A molded body which was heated at 140 ° C. for 5 minutes and then molded into a cylindrical shape,
After forming the positive electrode material into a cylindrical shape as in Example 2,
A stress was applied from the side to each of the molded body heated at each of 00 ° C., 120 ° C., 140 ° C., and 160 ° C. for 5 minutes, and each of the cylindrical forming bodies that were not heated according to the related art as in Comparative Example 1. The stress was gradually increased, and the stress value when the molded body was broken was measured. Table 1 shows the results.
Shown in

[0024]

[Table 1]

As apparent from the results shown in Table 1, 10
By heating to 0 ° C. or higher, the positive electrode material is firmly bound, the strength of the molded body is increased, and the stress value before the molded body is broken increases. From this result, it can be seen that cracking and chipping of the positive electrode during the manufacturing process are reduced and productivity is improved.

Next, the batteries of Examples 1 and 2 and the battery of Comparative Example 1 were discharged at 20 ° C. and a resistance of 2 Ω, and the discharge duration time until the terminal voltage of the battery dropped to 0.9 V was measured.
Table 2 shows the results. The measurement of the discharge duration was performed for the batteries of Examples 1 and 2 and Comparative Example 1 after the batteries were manufactured immediately after storage and after storage at 80 ° C. for 5 days (in Table 2, “80 ° C. 5
Days) and after storage at 80 ° C. for 8 days (shown in Table 2 as “80 days after 8 days”). As described above, the degree of swelling of the positive electrode when stored at 80 ° C for 5 days is the same level as when stored at 20 ° C for 3 years, and the degree of swelling of the positive electrode when stored at 80 ° C for 8 days is 20 ° C. Experience shows that it is at the same level as when stored for 5 years.

[0027]

[Table 2]

As shown in Table 2, the sample heated at 100 to 140 ° C. had a longer discharge duration and a shorter discharge duration due to storage than the non-heated sample as in Comparative Example 1. Was few.

In the above embodiment, the case where polyethylene is used as the binder is exemplified. However, like polyethylene, polytetrafluoroethylene, sodium polyacrylate, polyvinyl alcohol, styrene butadiene rubber, etc., whose binding effect increases by heating, are used. Even when used as a binder, the same effects as those of the polyethylene shown in the examples can be obtained.

[0030]

As described above, in the present invention, by increasing the binding effect of the binder by heating,
The strength of the positive electrode was increased, the productivity was improved, the swelling of the positive electrode during storage was suppressed, the decrease in the discharge duration due to storage was suppressed, and the reduction in battery capacity was able to be prevented.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a positive electrode in an alkaline dry battery of the present invention.

FIG. 2 is a partial cross-sectional view showing an example of the alkaline dry battery of the present invention.

FIG. 3 is a manufacturing process diagram of a positive electrode of a conventional alkaline dry battery.

[Explanation of symbols]

 1 positive electrode 3 separator 4 negative electrode

Continuation of the front page (72) Inventor Ryu Nagai 1-1-88 Ushitora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd.

Claims (4)

[Claims] An alkaline dry battery manufactured by heating a cathode material containing a binder to a temperature close to the melting point or softening point of the binder to increase the strength of the cathode. 2. The alkaline dry battery according to claim 1, wherein the binder is polyethylene and the heating temperature is 100 to 140 ° C. 3. A method for manufacturing an alkaline dry battery, comprising heating a positive electrode material containing a binder to a temperature close to the melting point or softening point of the binder to increase the strength of the positive electrode, and manufacturing the alkaline dry battery. 4. The method according to claim 2, wherein the binder is polyethylene and the heating temperature is 100 to 140 ° C.